Production of octadiene and dodecatrienes

ABSTRACT

PRODUCTION OF OCTADIENES AND DODECATRIENES BY ELECTROLYSIS OF A BUTADIENE IN THE PRESENCE OF A LOWER ALIPHATIC ALCOHOL AND AN ELECTROLYTE SALT USING GRAPHITE ELECTRODES.

United States Patent "ice 3,677,915 PRODUCTION OF OCTADIENE AND DODECATREENES Hans Schaefer, Eddigehansen, Germany, assignor to Badische Anilin- & Soda-Fabrik, Aktiengesellschaft, Ludwigshafen am Rhine, Germany No Drawing. Filed Aug. 26, 1970, Ser. No. 67,225 Claims priority, application Germany, Sept. 1, 1969, P 19 44 279.6 Int. Cl. C07b 29/06 U.S. Cl. 204-59 R 8 Claims ABSTRACT OF THE DISCLOSURE Production of octadienes and dodecatrienes by electrolysis of a butadiene in the presence of a lower aliphatic alcohol and an electrolyte salt using graphite electrodes.

This invention relates to a process for the production of octadienes and dodecatrienes by electrolysis of butadienes.

It is known from Chem. Rev. 68,471 (1968), that transl,4-dimethoxy-1,4-diphenyl-2-butene is obtained by electrolysis of 1,4-diphenylbutadiene in the presence of methanol and potassium hydroxide using platinum electrodes. It was therefore not to be expected that dimerization would take place in the electrolysis of butadienes.

It is an object of this invention to provide a process by which octadienes and dodecatrienes which hitherto have been accessible only with difiieulty are obtained in a simple manner.

In accordance with this invention this and other objects and advantages are achieved in a process for the production of octadienes and dodecatrienes by electrolysis of butadienes in the presence of a lower aliphatic alcohol and an electrolyte salt wherein graphite electrodes are used.

Preferred butadienes may bear, as substituents, one or two phenyl radicals and particularly one or two alkyl radicals having one to four carbon atoms. Butadiene itself has special significance. Examples of suitable starting materials are 1,4-diphenylbutadiene, isoprene and butadiene.

The electrolysis is carried out in the presence of a lower aliphatic alcohol, particularly an alkanol having one to three carbon atoms. Methanol has proved to be particularly suitable. It is advantageous to use one mole to three moles of alcohol for each mole of butadiene.

Electrolyte salts are used during electrolysis to improve conductivity. Alkali metal iodides, perchlorates or methylates or mixtures of two or more of these give good results. Sodium iodide, sodium perchlorate or sodium methylate have proved to the particularly suitable. It is advantageous to use such an amount of electrolyte salt that its concentration in the mixture to be electrolyzed is from 1 to 10% by weight, particularly from 2 to 8% by weight.

Electrolysis is advantageously carried out at a temperature of from 40 to +40 C., particularly from 30 to +10 C., at an anode potential of from +0.5 to +2.0 volts (measured against a silver/ silver chloride electrode), particularly from +0.6 to +1.8, and at a current density of from 25 to 75 milliamps/cmfi.

The use of graphite electrodes is an essential feature of the invention. Commercially available graphite electrodes which are suitable for electrolytic purpose are generally used.

The process according to the invention may be carried out for example by placing in a suitable electrolysis vessel provided with graphite electrodes spaced 10 mm. apart a mixture of the said butadienes and alcohols in the specified ratios and also the said amounts of electrolyte salts and carrying out the electrolysis under the specified conditions. It is advantageous to recycle the mixture being 3,677,915 Patented July 18, 1972 electrolyzed during electrolysis in order to achieve efficient mixing. It is possible to carry out the electrolysis with or without a diaphragm but it is advantageous not to use a diaphragm. Electrolysis is generally carried on until a consumption of from 0.1 to 0.5 Faraday has been reached. After the electrolyte salt has been separated, the mixture is worked up by conventional methods, for example by distillation.

Octadienes and dodecatrienes prepared by the process according to the invention are suitable for the production of conjugated polyenes, for example by elimination of methanol by treatment with polyphosphoric acid.

The invention is illustrated by the following example.

EXAMPLE A solution of 8 g. of sodium perchlorate in 60 g. of butadiene and 120 ml. of methanol is electrolyzed at 16 C. and an anode potential of +1.7 volts and a current density of 30 milliamps/cm. using graphite electrodes up to a consumption of 0.38 Faraday. The methanol is then distilled off and the residue has 20 ml. of water added to it. The product is extracted with ether and the ethereal extract fractionally distilled after the ether has been distilled off. Two fractions are obtained:

(a) Boiling point to C. at 14 mm. (14 g.).

(b) Boiling point 95 to C. at 0.01 mm. .(7 g.).

Fraction (a) consists, according to gas chromatographic analysis, of one third each of trans,trans-1,8-dimethoxyoctadiene-2,6, 3,6-dimethoxyoctadiene-1,7 and trans-1,6- dimethoxyoctadiene-2,7.

Fraction (b) consists according to gas chromatographic analysis mainly of trans-1,1Z-dimethoxydodecatriene-2,5, 9 and 1.lO-dimethoxydodecatriene-2,6,11.

I claim:

1. A process for the production of octadienes and dodecatrienes which comprises carrying out with graphite electrodes the electrolysis of a diene selected from the group consisting of butadiene and butadiene substituted once or twice by alkyl of 1 to 4 carbon atoms in the presence of a solvent reaction medium consisting essentially of a lower alkanol and an electrolyte salt selected from the group consisting of alkali metal iodides, perchlorates and methylates.

2. A process as claimed in claim 1 wherein an alkanol having one to three carbon atoms is used.

3. A process as claimed in claim 1 wherein 2 to 3 moles of an alkanol having one to three carbon atoms is used for each mole of butadiene.

4. A process as claimed in claim 1 wherein the concentration of electrolyte salt in the mixture being electrolyzed is from 1 to 10% by weight.

5. A process as claimed in claim 1 wherein sodium iodide, sodium perchlorate or sodium methylate is used as the electrolyte salt.

6. A process as claimed in claim 1 wherein the electrolysis is carried out at an anode potential of +0.5 to +2.0 volts.

7. A process as claimed in claim 1 wherein the electrolysis is carried out at a current density of from 25 to 75 milliamps per cmF.

8. A process as claimed in claim 1 wherein temperatures of from -40 to +40 C. are maintained.

References Cited Electrochemical Oxidation of Organic Compounds, by N. L. Weinberg et al., Chem. Reviews, vol. 68, 1968, p. 471.

JOHN H. MACK, Primary Examiner R. L. ANDREWS, Assistant Examiner 

